This invention relates generally to injection molding and more particularly to injection molding apparatus with integral cooling in a forward portion of the nozzle.
As is well known, the thermal characteristics of a hot runner injection molding system or apparatus is critical to its successful operation. This is particularly true with the increasing use of more temperature critical materials and even more particularly true for temperature assisted or thermal gating. Nozzles having integral electrically insulated heating elements are also known and a recent example is shown in the applicant's Canadian patent application serial no. 2,030,286 filed Nov. 19, 1990 entitled "Injection Molding Nozzle Having Tapered Heating Element Adjacent the Bore."
More recently, improved temperature control has been achieved by providing cooling around the forward end of the nozzle. Examples of this are shown in U.S. Pat. No. 4,622,001 to Bright et al which issued Nov. 11, 1986, the applicant's U.S. Pat. No. 4,911,636 which issued Mar, 27, 1990, Mold-Masters Limited Canadian patent application serial number 606,082 filed Dec. 5, 1988 entitled "Injection Molding System Having Fluid Cooled Inserts", and the applicant's Canadian patent application serial no. 2,022,120 filed Jul. 27, 1990 entitled "Injection Molding Cooled Socket Holder for a Heated Nozzle." However these arrangements all have the disadvantage that an additional insert or member is required to provide the cooling around the nozzle. U.S. Pat. No. 4,687,613 to Tsutsumi which issued Aug. 18, 1987 does show a type of nozzle with integral heating and cooling. However, in addition to being very difficult if not impossible to manufacture, this arrangement has the disadvantage that the integral cooling fluid passages run from near the rear end to near the forward end. This causes problems of excessive thermal expansion and contraction, particularly for temperature assisted or thermal gating applications.